The present invention relates to rail assemblies, and more particularly to a homing device and interlock for a rail assembly.
Telescopic rails, or drawer slides, are widely used for guiding movement of drawers, shelves, and other sliding elements. One common application for telescopic rails is to guide movement of drawers in a lateral filing cabinet. A conventional lateral filing cabinet includes multiple drawers stacked one above the other (See FIG. 1). Each drawer 210, 212 and 214 is typically attached to the cabinet by a pair of telescopic rails 216, 218 and 220, one located at each end of the drawer. The telescopic rail includes a cabinet member 222 that is attached to the cabinet 200, a drawer member 226 that is attached to the drawer 212, and an intermediate member 224 that is positioned between the cabinet and drawer members (See FIG. 2). The drawer member 226 is telescopically received within the intermediate member 224 which is, in turn, telescopically received within the cabinet member 222. A bearing assembly (not shown), such as a ball cage, or other friction reducing components are sandwiched between the rails to provide smooth and easy movement of the drawer. In some applications, the intermediate member is eliminated and the drawer member is received within the cabinet member.
In applications that include multiple drawers or shelves, such as a lateral filing cabinet, it is often important to prevent more than one drawer from being drawn out of the cabinet at a time. If more than a single drawer is drawn out, there is an increased likelihood that the weight of the items contained in the drawer will upset the balance of the cabinet and cause it to tip forward. This is a well-known problem that is typically addressed by providing the cabinet with an "interlock." Interlocks are available in a variety of different constructions. One such construction is a "stacked bar" construction, which includes a number of stacked locking bars located adjacent to the telescopic rails (See FIGS. 1 and 2). The locking bars 202, 204 and 206 are arranged so that the bottom of each locking bar is generally aligned with a corresponding rail 216, 218 and 220, respectively, and are free to move vertically. An inclined surface 208 is formed at the bottom of each locking bar 202, 204 and 206 facing the corresponding rail 216,218 and 220, respectively. To actuate the locking bars 202, 204 and 206, a ramp 230 is formed on the intermediate member 224 of each rail 216, 218 and 220. The ramp 230 is in horizontal alignment with the inclined surface 208 at the bottom of the corresponding locking bar 202,204 and 206. When a drawer 212 is opened, the ramp 230 moves horizontally and, through interaction of the ramp 230 and inclined surface 208, lifts the locking bars 202 and 204 located above that slide (See FIG. 2). As a result, the inclined surfaces 208 of the locking bar 202 located above the open drawer are no longer aligned with the corresponding ramps 230. This prevents any drawers located above the open drawer from being opened. Also, the ramp 230 of the open drawer obstructs upward movement any locking bars 206 located below the open drawer. This prevents any drawers located below the open drawer from being opened.
Another common feature in many telescopic rails is a "homing device." A homing device is a mechanism that biases the rail, and consequently the drawer or shelf, in a closed position. Like interlocks, homing devices are available in a variety of different constructions. One particularly ingenious design includes a homing device 300 that is mounted to the rear of the cabinet member (See FIGS. 3 and 4). The homing device 300 includes a base 302 and a pivot arm 304 that operatively interacts with the drawer member (not shown). The homing device 300 further includes a bias clip 306 that secures the pivot arm 304 to the base 302. The bias clip 306 and pivot arm 304 are arranged in a conventional "over-center" relationship so that the bias clip 306 biases the pivot arm 304 in both open (See FIG. 4) and closed position (See FIG. 3). When the drawer is closed, the bias clip 306 biases the pivot arm 304 in the closed position, thereby biasing the drawer in the closed position. When the drawer is opened, the pivot arm 304 pivots against the bias clip 306 until it passes its center point. After which, the bias clip 306 biases the pivot arm 304 in the open position, permitting the drawer to be fully opened. When the drawer is reclosed, the drawer member causes the pivot arm 304 to pivot back against the bias clip 306 until it passes back over its center point. After it has passed back over its center point, the bias clip 306 biases the pivot arm 304 in the closed position, thereby biasing the drawer in the fully closed position.
Although existing interlock and homing device constructions provide acceptable operation, a continuing need exists for more efficient and effective constructions. In particular, a need exists for effective interlock and homing devices that are easily and inexpensively manufactured and installed, and that require a minimum of modification to existing rail systems.